Machines, including vocational vehicles, off-highway haul trucks, motor graders, wheel loaders, and other types of large machines associated with construction, mining, and other industries often include operator positions that can be elevated significantly above ground level. The operator position may sometimes be accessible via an intermediate elevated entry position (e.g., a location on the rear bumper surface of a wheel loader) that may be somewhat closer to the ground. Intermediate entry position may be linked to the operator position via a set of stairs or other suitable access device. However, in some instances, even the intermediate elevated entry position may be five feet—or greater—above ground level.
To enable operators to access such elevated entry positions, stationary, fold-out, or other similar steps or ladders have often been provided leading to the elevated entry position on the machine. An operator may mount the ladder and climb up to the elevated entry position using hands and feet. When using such a method to access the elevated entry position, it is preferred that three points of contact be maintained for stability. For example, two hands and a foot or two feet and one hand should remain in contact with the ladder to maintain a stable climbing environment. However, maintaining three points of contact can make carrying items such as toolboxes, lunchboxes, papers, and other items up to the operator position of the machine difficult.
One device for accessing an elevated entry position of a machine is disclosed in U.S. Pat. No. 5,092,617 to Jones, Jr. (“the '617 patent”). The '617 patent discloses a step orthogonally mounted to a pneumatic piston and affixed to a cab of a machine. The device allows an operator to mount the step and actuate a lifting mechanism associated with the pneumatic piston, thereby lifting the operator to the level of the cab.
While the device of the '617 patent may assist an operator in reaching the level of an elevated operator position, the device presents several problems. First, by mounting to the exterior of the machine, the device may expand the envelope of the machine thereby risking collision with and/or sustaining damage from external objects (e.g., wall or doorway of a repair bay). Further, because the device of the '617 patent lacks any system for determining an operational condition of the machine, the device may be operated and/or self operate while the machine is in motion. Such operation may lead to dangerous conditions for both the operator and those surrounding the machine.
The present disclosure is directed at overcoming one or more of the problems or disadvantages in the prior art powered access devices.